Apparatus for assembling built-up pads with corrugated paperboard



G.BERUANT Nov. 5, 1957 APPARATUS FOR ASSEMBLING BUILT-UP PADS WITH CORRUGATED PAPERBOARD 4 Sheets-Sheet 1 Filed Nov. 10, 1955 G. BERLIANT APPARATUS FOR ASSEMBLING BUILT-UP PADS WITH CORRUGATED PAPERBOARD Nov. 5, 1957 4 Sheets-Sheet 2 Filed Nov. 10, 1955 Nov. 5, 1957 BERLIANT 2,812,006

APPARATUS FOR ASSEMBLING BUILT-UP PADS WITH CORRUGATED PAPERBOARD Filed NOV. 10, 1955 4 Sheets-Sheet 3 II ,I" 2

150 fimwewiv/ 14 Q91 0; a M -r M nited States Patent Dfiice 2,812,006 Fatented Nov. 5, 1957 APPARATUS FQR ASSEMBLING BUILT-UP PADS WETH CURRUGATED PAPERBOARD George Berliant, Sirolrie, iii, assignor to Stone Container Corporation, Chicago, Ill., a corporation of Illinois Application November 10, 1955, Serial No. 546,178

16 Claims. (Cl. 1541.6)

This invention relates generally to apparatus for use in the manufacture of pad structures for paperboard cartons and more particularly is concerned with a device for assembling glued, corrugated, built-up pads.

Paperboard containers for specific articles as opposed to containers for bulk goods, in most instances require padding of various kinds. Household appliances in particuiar, and other apparatus and equipment which have protuberances or ornamental finishes likely to become damaged if the containers are handled roughly, require padding. Such padding functions to space the article or apparatus within the container to prevent its shifting therein, and likewise serves as protective shock-absorbing cushions to prevent damage.

Many types of padding are used in modern containers, and, espectially in corrugated containers-an important factor is weight, strength and economy. It has therefore become customary to form padding by attaching built-up blocks of corrugated strips or members to sheets of corrugated paper. Such blocks are made usually by laminating layers of corrugated paper and gluing the same together.

Padding of the type described above has heretofore been assembled by hand. It is known that glued surfaces must have pressure applied thereto in order that the maximum advantage may be taken of the adhesive qualities of the glue. Where no clamping is used it is necessary that larger amounts of glue be used, and where clamping is used, the cost of labor and handling involved increases the expense of producing pads.

This invention relates to apparatus which enables the laminated blocks of paperboard, commonly referred to as build-ups, to be placed upon a pad, automatically clamped thereto, and, thereafter automatically released so that the clamping mechanism no longer clamps the buildup to the pad, thereby enabling the pad to be removed from the apparatus.

It is accordingly the principal object of the invention to provide such a structure and thereby to eliminate the disadvantages inherent in the manufacture of paperboard ads. p A further object of the invention is to provide a structure in which a universal mounting is provided enabling the apparatus to be used for the assembly of various sizes of pads and build-ups.

Still a further object of the invention is to provide a structure for the manufacture of paperboard pads in which such pads may be produced on an assembly line basis by the use of automatic equipment, the build-ups being assembled to the sheets of paperboard at one station and automatically clzunped thereto, and the clamping devices being automatically relieved at another station thereby dropping the completed article at the second station.

Still a further object of the invention is to provide a structure in which there is provided a fixture or jig to which the paperboard member is applied in position to receive thereon the glued build-ups, the fixture or jig having automatic clamping means poised in open position until the said build-ups are applied, and rendered closed to clamping position by the action of placing the glued build-ups upon the paperboard member.

Still a further object of the invention lies in the provision of novel means for adjusting the positions of the clamping mechanisms relative to the jig or fixture.

Many other objects of the invention will become apparent as the description proceeds, in which a preferred embodiment of the invention has been described in considerable detail and illustrated in the accompanying drawings. It is emphasized that the invention lies not only in the particular jig or fixture which is illustrated and described for the handling and assembling of one pad, but as well in the combination of a plurality of such jigs or fixtures arranged on a continuous belt conveyor system or on a continuously moving assembly line arrangement, in which the clamping devices are automatically unloaded or opened at a station removed from that at which the assembled pad was formed.

In the drawings:

Fig. l is a plan developed view of a paperboard member of the type used in producing the pad by means of this invention.

Fig. 2 is a plan view of the same but having the various portions of the pad folded preparatory to re ceiving the build-ups thereon.

Fig. 3 is a perspective exploded view of the folded member of Fig. 2 having the build-ups poised in proper position for gluing.

Fig. 4 is a perspective view showing the assembled device in completed form.

Fig. 5 is a top plan view of the structure of Fig. 4 but having other operations performed thereon, applying additional padding members.

Fig. 6 is a top plan view of the invention embodied in a structure for producing the pads of Figs. 4 and 5, the same being shown mounted upon a conveyor system.

Fig. 7 is a fragmentary side elevational view of the leading edge of the structure of Fig. 6 with portions being shown in section, an unglued assembly such as that of Fig. 4 having been associated with the particular device preparatory to the same being operated to clamp the build-ups to the paperboard member.

Fig. 8 is a top plan view of that portion of the appara tus illustrated in Fig. 7.

Fig. 9 is a View similar to that of Fig. 7 but showing the arrangement of the parts of the structure following the operation of the clamping device to hold the build-ups to the paperboard member.

Fig. 10 is a sectional View taken generally along the line 10-10 of Fig. 8 and looking in the direction indicated, that is, towards the leading edge of the apparatus.

Fig. 11 is a semi-diagrammatic view showing a fra mentary side elevation of the conveyor system provided with upper and lower reaches to show the manner in which the clamping devices are released at the second station and dropped upon the second conveyor system running transverse of the conveyor system having the jigs or fixtures of the invention associated therewith.

The invention consists generally of a universal jig or fixture having mounted thereon four clamping devices, each of which is arranged to clamp one or more built up blocks of paperboard laminated together to an edge of a generally rectangular paperboard member. The clamping devices are individually mounted and adjustable so as to accommodate various sizes of paperboard members and various thicknesses of build-ups.

The jig or fixture may be upon a guide structure such as a moving conveyor which either stops or slowly passes the station where the same is to be loaded. The operator or workman loads the conveyor by placing the rectangular paperboard member thereon, laying each of the build-ups at the proper position on the paperboard member after having glued the same. When the assembly is complete, the workman merely presses down upon the build ups and a trigger arrangement automatically snaps the clamping devices into engagement with the build-ups, thereby securely and firmly clamping the build-ups to the corrugated paperboard member. The fixture with its clamped build-ups is then moved to a second station, the time of transmission being sufiicient for the glue to set. At the second station by virtue of the construction of the clamping devices, a release is engaged which automatically releases each of the clamping devices and sets them in latched condition to be used once more. The two positions may be along a single line of a conveyor system or may be on an endless conveyor system in which the first station is at the top reach and the second station on the bottom reach, at which point the completed pads may drop out by gravity and fall either into a storage bin or upon another station where they can be carried to a different place for use.

Referring now to the specific details of the invention, attention is first invited to Figs. 1 through 5, in which there is illustrated the type of product which is capable of being manufactured by this invention. It is not intended by these illustrations and the description thereof to limit the use of the invention to the manufacture of the specific product since it will become apparent that the flexibility and universality of the device is such that it is capable of manufacturing a wide variety of pads using build-ups and paperboard sheets.

In Fig. 1 there is illustrated a generally rectangular paperboard member 20 provided along its edges with strips adapted to be folded to the condition which is shown in plan in Fig. 2. The particular structure comprises a central rectangular portion 22, narrow strips 24 and 26 of which 24 will become a base and 26 a side Wall of the folded structure, 28 and 30 of which 28 will become the base and 30 the side wall of the folded structure, 32 and 34 of which 32 will be the base and 34 another side wall of the folded structure, and 36 and 38 of which 36 will become a relatively wide base and 38 a side wall of the resulting folded structure.

Folding each of the strips 26, 30, 34 and 38 downwardly and then folding each of the strips 24, 28, 32 and 36 at right angles thereto, a structure such as shown in Fig. 2 results. The apparatus for doing this particular operation is of no concern here, since the same may be done on any folding machine or even manually if desired.

As shown in Fig. 3 built up blocks or build-ups are previously made from laminated paperboard held together by glue. This may be done in any desired manner such as for example, by making large sheets and thereafter cutting them to the desired size. In said Fig. 3 the blocks or build-ups are shown poised over the member 29 (only portions of which are visible in the figure) preparatory to laying the same upon the member ready for assembly. Thus there is a long strip 40 which is intended to engage the base 32 and side wall 34, there is a side strip 42 which is intended to engage the base 28, side wall 39, and a portion of the base 36, there is an opposite strip 44 which is designed to engage the base 24, side wall 26 and a portion of the base 36, and there are two blocks 46 which are intended to be positioned upon the ends of the base 36 in engagement also with the ends of the side wall 38 and portions of the buildups 42 and 44.

The completed structure is as clearly shown in Fig. 4 with the device being held in assembly by virtue of the build-ups having been glued in place. In Fig. the same structure has been modified by the addition of several strips of paperboard glued in position on top of the assembly of Fig. 4. For purposes of explanation hereinafter, the completed pad will be designated by the reference character 50. The additional strips 52 as shown in Fig. 5 are of no material importance to the invention or the resulting product.

Attention is invited now to Fig. 6 in which there is illustrated a jig or fixture 54 which is mounted on rollers 56 engaged in the tracks 58 of a conveyor system, the framework of which is generally designated 69. A driven chain 62, which moves to the left in Fig. 6, is connected with the jig 54 by means of a bracket 53 (Fig. 11) on the bottom of the jig secured to a link of the chain 62 and a tilt-limiting spring 64 connected between another such bracket 66 and a lug 68 (Fig. 10) on a link spaced from the bracket 53. In the particular construction illustrated the conveyor 60 is of the endless chain type and the jigs 54 are carried along a top reach which is shown in Fig. ll at 70 to the left hand end of the conveyor where a suitable. wheel returns the chain 62 along the bottom reach 72 with the jigs upside down as will be seen. Another wheel at the right hand end completes the circuit. The invention also is intended to include a structure in which there is no operation performed on the bottom reach of the conveyor. In the particular structure illustrated the pad assemblies 50 are dropped at a station while the chain is on its bottom reach.

Referring now to Fig. 6, it will be seen that the jig or fixture 54 is actually a carriage which moves along the conveyor by virtue of the rollers 56 moving in the track 58. The jig or carriage 54 is in the form of a rectangular support member or plate 74 having four pairs of tracks mounted thereon. Said pairs of tracks are designated 76, 77, 78 and 79. Each pair of tracks may be formed of elongated metal members illustrated in section in Fig. 10 which show tracks 77 having inwardly facing grooves 82 arranged to serve as guides for the tongues 84 mounted on the shoe 86.

There are four such shoes, each carrying a clamping device. The clamping devices are designated generally 90, 91, 92 and 93. All of the shoes and clamping devices are substantially identical in construction with one minor exception which will be explained hereinafter. It will suffice therefore to give a detailed explanation of one of such clamping devices and as will be seen hereinafter, the device which is positioned on the leading edge of the carriage 54 considering the direction of movement thereof will be set forth in some detail.

The tracks 76 will carry device 90 for serving the left hand side of the pad assembly 50, as viewed in Fig. 4, and the tracks 77, 78 and 79 cooperate with the clamp ing devices 91, 92 and 93 respectively for the other side of the pad assembly 50. It will be seen that the tracks 78 and 79 are aligned transversely of the carriage or jig 54 while the tracks 76 and 77 are aligned parallel with the direction of movement of the said carriage 54. As a matter of fact, it is economical and convenient to form the tracks 76 and 77 of the identical elongate metal members.

It will be seen that the plate 74 is composite, that is, made up of more than one layer, although this is merely a matter of design. The base 96 may be formed of plywood or the like, and may have narrow slots 98, 100, 102 and 104 cut therein to accommodate portions of the respective clamping devices 90, 81, 92 and 93 which extend downwardly therethrough and protrude from the bottom of the carriage 54.

It will be noted that the slot 98 like the others is substantially narrower than the width of the shoe 86 so that in addition to being guided by the grooves 82, the shoe 86 rides upon the top of the base 96. Secured to the top of the base there is provided a supporting plate 106 and a protective cover sheet 108, which together, have the thickness of the tracks 77 so that the top of the tracks is flush with the surface of the plate 74. The

various laminations of the plate 74 are held together by suitable screws such as those illustrated in Fig. 6. The construction of the plate 74 may be varied to a great extent.

The position of the shoe along the slot 98 is adjustable by virtue of a clamping connection between the shoe and a clamp block 110 disposed within the slot 98 and having flanged edges 112 as shown in Fig. adapted to engage the bottom of the base plate 96. A bolt 114 passing through a suitable opening in the shoe 86 at the end thereof is screw-threadedly engaged in the clamping block 110, such that loosening the bolt 114 enables the entire shoe to be moved along the slot 93 and positioned any desired place therein. The front end of the shoe 36 is provided with a pair of trunnions 116, and a generally L-shaped lever or rocker arm 118, having upper portion or arm 119 and lower portion or arm 120 extending into the slot 98, is pivotally mounted upon the trunnions 116 by means of a pivot pin 122. The lower end of the lever arm 120 is provided with a roller 124 mounted upon a bracket 126 which is secured to the arm 126.

The arrangement of the roller 124 is such that its axis is transverse the line of movement of the carriage 54 for a purpose to enable release of the clamping device in a manner to be described. The only difference between the clamping devices 90 and 91 and those designated 92 and 93 reside in the arrangement of the roller 124. Although the clamping devices 92 and 93 are provided with substantially the identical rocker arm 118 and the rocker arms during pivotal movement pivot on axes at right angles to the axis of the pin 122, the axes of the rollers mounted on the said clamping devices 92 and 93 are parallel with the axis of the roller 124, so that the same release mechanism will operate to release these clamping devices like the devices 90 and 91. It has not been necessary to illustrate the arrangement of roller relative to the rocker arm although this may be understood if one merely rotates the axis of the roller 124 through 90 degrees in a horizontal plane.

; Midway between the ends of the shoe 86 on the bottom thereof there is provided a pair of relatively small cars 130 which have the trigger member or latch 132 pivotally mounted on a pin passing therethrough at 134. The trigger member or latch 132 is provided at its rear with a projection 136 carrying a spring cavity 138 therein. The bottom of the shoe 86 is provided also with an aligned spring cavity 140 and a coil spring 142 is disposed between the two cavities 138 and 140 arranged to bias the trigger 132 in such a direction as to rotate the trigger or latch clockwise about the pin 134. On its left hand side the trigger member 132 is provided with a shoulder or tooth 144 which is arranged to cooperate with the extension or tooth end 146 of the arm 126. When in the position shown in Fig. 7 the L-shaped lever 118 is biased to rotate in a clockwise direction about the pin 122 by virtue of a relatively strong coiled spring 148 extending between the projection 150 formed on the upper edge of the lever arm 120 at a suitable seat 152 provided in the bottom of the shoe 86. When the clamping device is disposed as shown in Fig. 7, further rotation of the lever arm 118 caused by the spring 148 is prevented because of latching engagement between the end 146 and the shoulder 144. If however, the trigger or latch 132 is rotated in a counter-clockwise direction against the pressure of the'spring 142, the shoulder 144 will move out from beneath the end 146 relieving the latching engagement and the spring 148 will be enabled to rotate the lever arm 118 in a clockwise direction.

The upper arm 119 of the lever 118 is provided with a pair of laterally extending wings 154 which may be integrally formed therewith. A support block 156 is screwed to the wings 154 by means of the machine screws 158, and an angle shaped pressure member 160 or jaw of elongate formation is engaged upon the block 156 and over the top of the wings 154. When the lever arm 118 rotates in a clockwise direction the pressure member or jaw will be pressed against any obstruction which may be in its way.

The shoe 36 has a vertical passageway 162 bored therein provided with an enlarged diameter cavity at its upper end as shown at 164. A button 166 is mounted in the said cavity having a stem 168 protruding downwardly through the opening 162. The length of the stem 168 is such that in the position illustrated in Fig. 7 the head 166 protrudes above the surface of the sheet 1%. Means may be used to prevent the button 166 from dropping out when the carriage 54 is upside down, but the same is not necessarily illustrated. The trigger 132 is provided at its upper end with a projection 170 which engages the shoe at the bottom end of the passageway 162 preventing the downward movement of the stem 168 of the button 166. In the condition shown in Fig. 7 if pressure is applied downwardly upon the button head 166, such as by manual depression of said button the projection 170 will be engaged and the trigger 132 rotated in a counter-clockwise direction about the pin 134 releasing the end 146 and causing the spring 148 to rotate the lever arm 118.

The shoe 36 is provided at the top thereof with the inside guide member 172 in the form of an elongate angle iron held in place relative to the shoe 86 by means of a bolt 174 engaging in the shoe through slot 176 formed in the guide member 172. Any suitable guide arrangement or pressure receiving device or support member may be used in place of the angle member 172. The particular structure using the angle member 172 is for use in the assembly of pad assemblies of the type shown, in Figs. 1 through 5.

It should be obvious that the distance between the inside guide member 172 and the left hand end of the shoe 56 may be adjusted by loosening the bolt 174.

In using the apparatus the assembly of the parts of the pad structure 56 may be laid upon the jig or fixture 54 and built up thereon the fixture 5 functioning as a planar supporting member or bed for the pad. The workman applies the glue to the various build-ups and presses the build-ups into position, thereby releasing the clamping devices one at a time. If desired, there is sufiicient pressure against the push member or button 166 to support the weight of the various parts so that the entire assembly may be placed on the jig and all of the buttons pressed then. In the case of the edge of the structure 50 which included the build-ups 46, they may be placed in position and the workman merely presses with his finger upon the center of the base 36 to cause operation of the clamping device 98 positioned thereat.

Once the build-ups have been clamped in position, the conveyor chain 62 moves the assembly down the conveyor 61) to the second position which in this case is associated with the bottom reach of the conveyor. As shown in Figs. 6 and 11 there is a support member 186 which is secured across the conveyor and the same may have one or more release plates 182 secured to the same. Preferably the release plates 182 are in the form of angle irons having a bottom plate tilted slightly downward, it being appreciated that the carriages 54 pass by this point upside down so that the rollers 124 are pointing upward. When the rollers engage the plates 132 they are pushed inwardly against the pressure of the spring 148,

Once the end 146 has passed the shoulder 144, the spring 142 snaps the trigger in a clockwise direction as viewed in Fig. 9 beneath the extension or projection 146 and thereby latching the clamping device to open position as shown in Fig. 7. Obviously, the moment the jaw 166 has been moved out of engagement with the various build-ups, the structure 51 will drop from the carriage. A conveyor system 185 may be provided to carry the structure 50 to another station. Obviously, since the rollers of the various clamping devices wili be engaged thereby rotating the lever 118 in a counter-clockwise direction.

at different times, first the leading edge of the structure 50 will be released followed by the remainder.

Various structures may be associated with the apparatus described without in any way affecting the advantages and salutary objects achieved. Furthermore, considerable variation in the structure itself may be made without in any way departing from the spirit and scope of the invention as set forth in the appended claims.

What it is desired to secure by Letters Patent of the United States is:

1. Apparatus for assembling paperboard pads which have at least one build-up adhered to a sheet member which comprises, a support for having said sheet member positioned thereon, a clamping device secured to the support and including a rocking member with a jaw above the support and an arm below the support, means biasing the arm to rock the member in a direction to press the jaw into engagement with the top of the support to clamp a build-up to said sheet member upon said support, a spring-pressed latch engaging said arm to prevent rotation of the rocking member, and manually operable means accessible from the top of said support for moving said latch out of engagement with said arm to cause operation of said clamping device.

2. Apparatus as claimed in claim 1 in which the manually operable means comprises a rigid member extending through the support having its lower end engaged against said latch and its upper end protruding above said support adjacent said jaw when said latch is engaged with said arm, and adapted to be moved downward to disengage said latch by pressing on said protruding end.

3. Apparatus as claimed in claim 1 in which said arm has a depending extension adapted to be moved in a direction causing latching engagement between the latch and arm.

4. Apparatus as claimed in claim 1 in which said clamping device is mounted on a shoe and said support has a track to enable said shoe to be slid to difierent positions along said track and means for removably securing said shoe in any desired position.

5. Apparatus for assembling paperboard pads which have at least one build-up adhered to a sheet member which comprises, a carriage adapted to be moved between a clamp engaging station and a clamp releasing station of a conveyor, said carriage having a bed for receiving said sheet member thereon, a slot in the bed, a rocker arm pivoted for movement in the slot and having a clamping jaw on its upper end, means biasing it to move the clamping jaw against the bed, and a spring pressed latch on the bottom of the bed engaging the lower end of the rocker arm to prevent said movement thereof, a pushbutton extending through the bed and out the top thereof engaging the latch to move same against its spring out of engagement with said lower end, and said lower end of said rocker arm also having means for engaging an obstruction at said clamp releasing station to move said rocker arm in a direction to disengage said clamping jaw and cause re-engagement of said latch.

6. Apparatus for assembling paperboard pads which have at least one build-up adhered to a sheet member on the surface of said sheet member along one edge thereof, which comprises a generally horizontal planar support member having means on the upper face thereof seating said sheet member thereon and including a pressure-receiving member spaced from a line defined by the said one edge of said sheet member when same is so seated, in a direction inward of said sheet member edge, said pressure-receiving member extending upward from the support member, an opening in said planar member having a rocker lever pivoted therein with upper and lower arms respectively extending above and below the upper face of the support member, an elongate jaw secured to the upper arm parallel to said line, a tooth on the lower arm and means spring-biasing the rocker lever to pivot in a direction moving the jaw toward said line germs 8 from a point spaced therefrom opposite said pressurereceiving member, said jaw when permitted to move toward said line serving to clamp a build-up placed adjacent said line between itself and said pressure-receiving member, a spring-pressed latch engaging said tooth when said jaw is away from said line in non-clamping position and preventing pivotal movement of said lever, a push-member having a part protruding from the top of the support member between said line and said pressure-receiving member and adapted to be covered by that portion of said sheet member receiving said build-up thereon, and said push-member extending into engagement with said latch and adapted to move same to unlatching position when the protruding part is pushed down, as by the place ment of said build-up in position.

7. Structure as claimed in claim 6 in Which means are provided to return the jaw to non-clamping position and causing the latch to once more engage said tooth, comprising an extension on the rocker lever adapted to be engaged to move said rocker lever against the bias of said spring-biasing means.

8. Apparatus as described in claim 1 in which there are a plurality of clamping devices secured to said support for assembling a plurality of build-ups to said sheet member, and the clamping devices are constructed as said first mentioned clamping device.

9. Apparatus for assembling paperboard pads, said pads each comprising a rectangular sheet of paperboard having at least one build-up adhered to the surface of said pad along an edge thereof, comprising, a conveyor having a flexible drive member moving along the same, a carriage secured to said drive member for movement therewith and the conveyor having means for guiding the carriage in its movement, said carriage having a bed, means on the bed seating a sheet of paperboard thereon, a pivotal jaw biased to move against an edge of said sheet, to clamp a build-up to said sheet, a spring latch on said carriage normally latching said jaw in non-clamping position, pressure-operated latch-relieving means on the carriage, means connected with said jaw extending from said carriage, and said conveyor having a re-set member in the path of said extended means adapted to engage the same as the carriage is moved past said re-set member serving to move said jaw from clamping to non-clamping position and into re-engagement with said spring latch.

10. Apparatus as described in claim 9 in which the conveyor has two stations and a plurality of said carriages spaced along and secured to said flexible drive member and movable therewith along said conveyor, the stations comprising a clamping and a non-clamping station, the pressure-operated latch-relieving means adapted to be 0perated at one station in assembling the build-ups to said sheets, and the re-set member being positioned at said disassembly station, whereby when said jaws are moved to non-clamping positions, the completed pads may be removed from said apparatus.

11. Apparatus as claimed in claim 9 in which the latchrelieving means includes a button protruding from said bed and adapted to be covered by said sheet member whereby to be operated when said build-up is pressed onto the sheet member.

12. Apparatus as claimed in claim 9 in which said carriage has a slidably adjustable shoe thereon and said jaw, spring latch, and latch-relieving means are all mounted in fixed relation one to the other on said shoe and movable therewith to enable different dimension pads to be assembled with said apparatus.

13. Apparatus for assembling paperboard pads, each pad comprising a rectangular sheet having at least one block adhered to the surface thereof along an edge, and which comprises a confined elongate guide structure, a carriage movable along said structure from a first to a second station, said carriage having an upper supporting Surface provided with an elongated sheet guide member 9 for seating said sheet in proper position thereon, a track, a shoe slidable in said track below said upper surface and the carriage having a slot accommodating sliding movement of said shoe, means for fixing said shoe in any desired position, said guide member being mounted on said shoe transverse of the direction of slidable movement thereof, a rocker lever mounted on said shoe and having an upper arm and a lower arm below said upper surface, the upper arm having an elongate jaw thereon parallel with the guide member and being movable between a clamping position spaced from said guide member a distance less than the thickness of said block and sheet combined, and a non-clamping position spaced from said guide member a distance greater than the thickness of said block and sheet combined, means on said shoe biasing said lever to move the jaw into clamping position, but said shoe having a spring-trigger member normally engaging said lower arm and holding the lever with the jaw in non-clamping position, a trigger release member exposed on said upper surface and adapted to be engaged by the sheet when said block is manually pressed against the same to release the trigger and simultaneously cause clamping of said block to said sheet, and means for moving said lever back to a position where the trigger once more engages the same.

14. A structure as described in claim 13 in which the last means comprises a second lever connected with the lower arm, and a trigger setting projection on said guide structure located at said second station and adapted to engage said lever and move the same as the carriage moves past said second station.

15. A structure as described in claim 14 in which the last means comprises a roller on the lower arm and an inclined plane member on the guide structure at the second position adapted to be engaged and ridden by the roller to cause swinging of said rocker lever against its biasing means.

16. A structure as described in claim 15 in which the guide structure has upper and lower parts and a flexible endless drive member with upper and lower reaches having the carriage secured thereto to be moved in continuous path along the upper reach erect and along the lower reach upside down, and said second station being located at said lower part of said guide structure.

References Cited in the file of this patent UNITED STATES PATENTS 1,909,513 Agar May 16, 1933 2,068,771 Sherman Jan. 26, 1937 2,504,473 Antwerpen Apr. 18, 1950 2,575,898 Tadinger Nov. 20, 1951 2,579,675 Kaplan et a1. Dec. 25, -1 

